ABSTRACT The goal of this project is to develop an optical sensor for anticoagulation self-testing in patients. Oral anticoagulant therapy is administered in millions of patients in the United States and worldwide for preventing venous and arterial thrombosis, the world's leading killer. Despite its effectiveness in reducing the incidence of acute thrombosis, if inadequately monitored, anticoagulation therapy can cause serious bleeding complications that can be life-threatening. Effective dosing of oral anticoagulants is often problematic due to the narrow therapeutic window between bleeding and coagulation, numerous food and drug interactions, variability in dose response among patients, and patient non-adherence. Anticoagulation testing is traditionally conducted using standard tests that measure prothrombin time (PT) and the associated international normalized ratio (INR). Unfortunately, these tests provide information limited to clotting time, and are often not sensitive enough to evaluate bleeding risk in anticoagulated patients. Furthermore, the increasing costs and long reporting times associated with laboratory testing, the rapidly growing patient population on anticoagulants, and the diminishing numbers of primary care physicians, together impose a staggering burden on primary care services for anticoagulation monitoring. These factors underscore the dire unmet need for rapid and comprehensive anticoagulation self-testing in the home. Our proposal directly addresses this need. Here, we propose to develop a palm-sized, optical sensor that provides multi-functional assessment of blood coagulation status in less than 5 minutes. The new optical sensor will be a smartphone compatible device and will quantify multiple relevant coagulation parameters including clotting time, thrombin generation rate and fibrin polymerization, at the push of a button. A custom blood test-strip, pre-treated with coagulation activators, will be fabricated that will require a drop of blood to measure a comprehensive coagulation profile from the real-time assessment of time-varying light intensity fluctuations. To validate the device, we will perform correlative studies in normal and anti-coagulated patient blood samples to test the accuracy and measurement sensitivity of the optical sensor via comparison with conventional laboratory tests. Given its low cost, rapid measurement time and capability for multifunctional coagulation assessment, the proposed optical coagulation sensor is poised to reduce the need for routine laboratory testing, increase the efficiency of primary care operations and empower patients to improve the quality of anticoagulation management.